Male ostrich

Ostrich is the one bird whose sex is easily determined visually. Once ostriches reach sexual maturity, it is easy to tell males from females. Full distinction between the sexes is reached at age of two. Body size and color of wing feather in males suggest a role in in recognizing the sex.

Males have black and white coloring at the age of two. While the grayish brown females and immature birds are less brilliant. When it is ready to mate, shines, beak, and neck of the bird turn bright red which is due to hormone secretion from testes of males.

 Red intensity is directly related to male sexual trait. Brightness and darkness of ostrich eggs are distinct indicator of its productivity. The ostrich is one of very few birds to have a penis. It is important to note that red bill and red parts in their back in males is dependent upon growth and development of the male reproductive tract striking. Black and white color of feathers is influenced by the absence of ovaries.

Male ostrich never gets red bill or body in case of infertility, while its feathers remains still black and white.